Baths for one-stage quick etches



United States Patent Ofitice 3,074,836 Patented Jan. 22, 1963 3,074,836BATHS EUR (ENE-STAGE QUICK ETCHES Abraham Isidor Sherer, Belleville, NJ., and John Ruzicka,

Brooklyn, N.Y., assignors, by mesne assignments, to

Bail Brothers Company, Incorporated, Muncie, Ind., a

corporation of Endiana No Drawing. Filed July 11, 1956, Ser. No. $7,062

Claims. (Cl. 156-8) This invention relates in general to etching bathsand processes for etching devices composed of metals such as zinc andmagnesium, and various alloys such as Zinc and magnesium alloys, andmore particularly to an improved bath and process for effecting aone-stage quick etch. This application constitutes acontinuation-in-part of application for patent Ser. No. 526,783, filedAugust 5, 1955, now abandoned.

Among the objects of the present invention, it is aimed to provide animproved bath or bath solution and process to effect a one-stage quicketch for etching various metals such as zinc and magnesium and variousalloys such as zinc alloys, magnesium alloys and the like, whichsolution can be produced at a minimum of cost as compared to the cost ofsolutions today used in baths for producing va quick etch, whichsolution is more stable than solutions today in use for producing aquick etch, which solution is more flexible, that is, the ingredients ofwhich can be varied relative to one another without materially changingthe end result obtainable, which solution and process is not accompaniedby objectionable odor such as is the case with the solutions today usedfor producing a quick etch, and which one-stage quick etch can becompleted in a minimum period of time.

As compared to the cost of solutions heretofore in use for effecting aone-stage quick etch which cost about double the cost of theconventional four to five stage etching baths containing only water andnitric acid, the cost of the present solution is only fifty percent morethan that of the conventional four to five-stage etching bath orseventy-five percent of the earlier one-stage solution.

As compared to the stability of the solutions heretofore in use foreffecting a one-stage quick etch which did not exceed eight hours, thepresent solution will remain effective for at least four days. In otherwords, the one-stage solutions today in use deteriorate by reaction ofthe ingredients with each other to the degree that the effect can beobserved on the results produced by the solutions, even after only onehour of standing without being used. This rate of deterioration is sogreat that the number of engravings which can be produced using thesolution is largely determined by the age of the solution. For exsideredunusuable the next day and is discarded, even if it has had little or nouse.

On the other hand, with the present solution, no effect of deteriorationdue to reaction of the ingredients with each other could be observed onthe results produced by the solutions after four days of standingwithout use. The practical result is that the number of engravings whichcan be produced by the present solution is determined ample, a freshsolution made one day is normally con- I only by weight of metaldissolved into the solution, not

tion proportionately could vary as much as 10% without affecting etchingefficiency.

As compared to the odor of solutions heretofore used for one-stage quicketching, the present solution is much less objectionable in odor. Thisodorless characteristic is of inestimable value in view of healthdepartment regulations of municipalities barring dumping of used ordeteriorated solutions of this type on account of their odor.

With all of the aforesaid advantages over solutions heretofore in use,the time period for effecting an effective etching process in aone-stage quick etch with the present solution will not exceed the sevento ten minutes required for effecting a one-stage quick etch of theprocess heretofore in use and in turn the time period for effecting anetching process with the present solution compares extremely favorablewith the forty-five to sixty minutes time period required to effect anefiicient etching process by the conventional long processes using threeto five stages.

In order to produce a satisfactory bath solution and process accordingto the present invention it was found necessary to mix nitric acid,water, a petroleum solvent and at least one wetting agent which is anessentially solvent soluble alkyl aryl sulphonate including the acidform as well as the'sodium salts of the same. An additional improvementin results is obtained by including a second' wetting agent, essentiallywater soluble, such as water-soluble alkyl aryl sulphonates. Aside fromthis improvement in results, the water-soluble wetting agent alsoreduces the possibility of a thickening of the solution, making itunusable, which possibility exists just beyond but not within thepreferred range of compositions of the bath. Basically, in addition toimproving results, its secondary function is that it adds to theflexibility of permissible variations in proportions of otheringredients and variations in mechanical conditions which can be used toproduce satisfactory results.

The solution so mixed is essentially a physical mixture, to wit, anemulsion, the ingredients of which do not react upon one anotherchemically when mixed in this four or five part group, in the interestof maintaining consistency of results obtained from the solution,without eifect by the age of the solution. The petroleum solvent vinthis mixture was selected in the interest of reducing tions set forth inthe following examples: 50

Example 1 v Parts by weight 42 B. nitric acid' c 10.7 150 F. flash"solvent, aromatics content 93% 7.9 Long chain alkyl aryl sulphonate,average molecular weight 450, average chain 'length of alkyl portion 18to 24 carbon atoms 0.18 Alkyl aryl sulphonate average chain length(alkyl portion), 12 carbon atoms- 0.04 Water 81.18

. Example 2 42 B. nitric acid 10.7 F. flash solvent, aromatics content90- 93% 7.12 Long chain alkyl aryl sulphonate, average molecular weight450, average chain length of alkyl portion 1 to 24 carbon atoms 0.12Alkyl aryl sulphonate, average chain length (alkyl portion 12'carbonatoms 0.00008 3 Example 3 42 B. nitric acid 11.8 150 F. flash solvent,aromatics content 90- 93% 7.9 Long chain alkyl aryl sulphonate, averagemolecular weight 450, average chain length of alkyl portion .18 to 24carbon atoms 0.16 Isopropyl napthalene sulphonate 0.15 Water 80.09

Example 4 42 B. nitric acid 13.0 150 F. flash solvent, aromatics content90- 93% a 7.8 Long chain alkyl aryl sulphonate, average molecular weight450, average chain length of alkyl portion 18 to 24 carbon atoms 0.18Sodium N-methyl-N-oleoyl taurate 0.04 Water 78.98

Example 5 42 B. nitric acid 11.8 150 F. flash solvent, aromatics content90- 93% 8.2 Long chain alkyl aryl sulphonate, average molec ular weight450, average chain length of alkyl portion 18 to 24 carbon atoms 0.16Technical lauryl sodium sulphate 0.02 Water 79.82 W

Example 6 42 B. nitric acid 11.8 Medium boiling range aliphatichydrocarbon aromatics content 7.2 Long chain alkyl aryl sulphonate,average molecular weight 450, average chain length of alkyl portion 18to 24 carbon atoms 0.22 Alkyl aryl sulphonate, average chain length(alkyl portion), 12 carbon atoms 0.06 Water 80.72

Although the water-soluble alkyl aryl sulphonate has been foundparticularly efiective in preventing thickening of the solution, atcertain concentrations of the other ingredients, good results have alsobeen achieved when the water-soluble alkyl aryl sulphonate has beenentirely omitted in the solution, as illustrated by the followingexample:

Similarly instead of omitting the water-soluble alkyl aryl sulphonateentirely, excellent results have been achieved when the water-solublealkyl aryl sulphonate was greatly reduced, as an instance,0.00005-0.0001 part by weight, as illustrated in Example 2.

It is to be noted that Examples 1 and 2 aforesaid recite diflerentproportions of the same ingredients and that in particular the usableproportions of solvent and solvent-soluble wetting agent depend upon theproportion of the water-soluble alkyl aryl sulphonate present in theformula.

The specific amounts of the ingredients listed in the aforesaid sevenexamples may be varied without appreciably changing the resultsproduced. As an instance, Examples 1 and 2 aforesaid may be changed asfollows:

Example 8 3-20 part nitric acid 1-12 part petroleum solvent, containing0100% aromatic solvent 0-100% aliphatic solvent 0.02-2.0 parts longchain alkyl aryl sulphonate with an average molecular weight about 450and an average chain length of 18 to 24 carbon atoms 02.0 parts alkylaryl sulphonates, with an average alkyl chain length of about 12 carbonatoms Remainder of the 100 parts total being water Example 3 aforesaidon the other hand may be changed as follows:

Example 9 3-20 parts nitric acid 1-12 parts petroleum solvent 0.02-2.0parts long chain alkyl aryl sulphonate with an average molecular weightof about 450 and an average chain length of about 18 to 24 carbon atomsin the alkyl portion 0-2.0 parts isopropyl napthalene sulphonateRemainder of the 100 parts total being water Example 4 aforesaid may bechanged as follows:

Example 10 3-20 parts nitric acid 1-12 parts petroleum solventcontaining 0-100% aromatic solvent 0.02-2.0 parts long chain alkyl arylsulphonate with an average molecular weight of about 450 and an averagechain length of about 18-24 carbon atoms in the alkyl portion 0-2.0parts of the reaction product of a fatty acid and an organic sulphonate,such as sodium-N-methyl-N- oleoyl taurate Remainder of the 100 partstotal being water Example 5 aforesaid may be changed as follows:

Example 11 3-20 parts nitric acid 1-12 parts petroleum solventcontaining 0-100% atromatic solvent 0.02-2.0 parts long chain alkyl arylsulphonate with an average molecular weight of about 450 and an averagechain length of about 18-24 carbon atoms in the alkyl portion 0-0.1 partalkyl sulphate, such as an alkali metal-salt of lauryl sulphateRemainder of the 100 parts total being Water While any of theconventional solvent-soluble alkyl aryl sulphonate Wetting agents todayin use could be used, excellent results have been achieved with thesolventsoluble alkyl aryl sulphonate wetting agent when it has thefollowing physical proper-ties, to wit: having a chain length of thealkyl portion of about 18 to 24 carbon atoms, an average molecularweight of 450, about 50 to 55% active ingredients, and about 45 to 50%free oil.

In turn, while any number of the well-known watersoluble wetting agentstoday in use could be used to advantage, excellent results have beenachieved with the water-soluble wetting agents known in the trade asNaccDonol NRSF, Aerosol OS, Igepon T-77 or Duponol ME The typicalphysical properties of these four watersoluble wetting agents are asfollows:

Naconal NRSF is a medium-chain alkyl aryl sulphonate, having an averagechain-length of the alkyl portion of about 12 carbon atoms, about 92%active ingredients, and the remaining 8% being essentially sodiumsulphate.

Aerosol OS is a short chain alkyl aryl sulphonate consisting of about80% isopropyl naphthalene sulpgonate and the remainder being essentiallysodium sulp ate.

The Igepon T-77 is an example of the product of the reaction of a fattyacid and an organic sulphate consisting of about 72%sodium-N-methyl-N-oleoyl taurate and the remaining 28% being essentiallysodium chloride.

The Duponol ME Dry is an alkyl sulphate consisting of about 90%technical lauryl sodium sulphate and the remaining being essentiallysodium sulphate.

While any one of the conventional petroleum-cut solvents today in usecould be used, excellent results have been achieved when any of thepetroleum-cut solvents known in the trade as Solvesso 150, Amsco Solv E,or Amsco 460 Solvent, was selected. The typical properties of thesethree petroleum-cut solvents are substantially as follows:

Properties Solvesso Arnsco Amsco 4G0 150 Solv E Solvent API Gravity 60 FSpec. Gravity 60 F Lbs. pei- Gallon Percent Aromatics While solutionsmade according to the present invention can be used to good advantage inetching devices or plates composed of a great variety of metals,excellent results have been achieved with Zinc and magnesium alloys.Examples of such alloys are as follows:

From the foregoing it will thus be seen that due to the fact that thevarious ingredients of the baths here disclosed merely form physicalmixtures in the form of emulsions as distinguished from chemicalinter-reactions the baths will remain effective for periods of at leasttwo weeks. It has been found, as an instance, that the alkyl arylsulphonates will not react chemically with any of the ingredients of thesolution but in the etching process will form a protective film toenable the acid of the solution to penetrate the exposed portions, thedepth necessary without any objectionable undercutting.

As is conventional with etching processes, the image to be formed inrelief on a device is coated with an acid resisting coating andthereupon the etching mixture is supplied either by splashing, sprayingor the like on the remaining exposed or unprotected faces of the device.In the present instance, the etching mixture is the mixture heretoforeset forth and constituting a part of the invention.

It is obvious that various changes and modifications may be made in theingredients and the percentages of ingredients aforesaid withoutdeparting from the general spirit of the invention as set forth in theappended claims.

We claim:

l. A bath solution for a one-stage quick etch on an alloy comprising byweight 3 to 20 parts nitric acid, 1

to 12 parts of a petroleum solvent, 0.2 to 2.0 parts long chain alkylaryl sulphonate, and 0.00008 to 2.0 parts alkyl aryl sulphonate having achain length of about 3 to 12 carbon atoms, and the remainder water.

2. A bath solution for a one-stage quick etch on an alloy comprising byWeight 11.8 parts nitric acid, 80.09

450 and a chain length of about 18 to 24 carbon atoms,

and 0.04 part sodium-N-methyl-N-oleoyl taurate.

4. A bath solution for a one-stage quick etch on an alloy comprising byweight 11.8 parts nitric acid, 79.82 parts water, 8.2 parts of apetroleum-cut solvent having an aromatic content of to 93%, 0.16 partlong chain .alkyl aryl sulphonate with a molecular weight of about 450and a chain length of about 18 to 24 carbon atoms, and 0.02 parttechnical lauryl sodium sulphate.

5. A bath solution for a one-stage quick etch on an alloy comprising byWeight 3 to 20 parts nitric .acid, 1 to 12 parts petroleum solvent, 0.02to 2.0 parts long-chain alkyl aryl sulphonate with an average molecularweight about 450 and an average chain length of 18 to 24 carbon atoms,0.00008 to 2.0 parts alkyl aryl sulphonate, with an average chain lengthof about 3 to 12 carbon atoms, and the remainder water.

6. A bath solution for a one-stage quick etch on an alloy comprising byweight 3 to 20 parts nitric acid, 1 to 12 parts petroleum solvent, 0.02to 2.0 parts long chain alkyl aryl sulphonate with an average molecularweight of about 450 and an average chain length of about 18 to 24 carbonatoms, 2.0 or less parts isopropyl naphthalene sulphonate, and theremainder water.

7. A bath solution for a one-stage quick etch on an alloy comprising byweight 3 to 20 parts nitric acid, 1 to 12 parts petroleum solvent,containing 0 to aromatic solvent, 0.02 to 2.0 parts long chain alkylaryl sulphonate with an average molecular weight of about 450 and anaverage chain length of about 18 to 24 carbon atoms, 0.1 part or lessalkyl sulphate, and the remainder water.

8. A bath solution for a one-stage quick etch on metal alloys comprisingby weight 3 to 20 parts of nitric acid, 1 to 12 parts of a petroleumsolvent, surface active agents consisting of 0.02 to 2.0 parts of asolvent soluble alkyl aryl sulphonate and 0.00008 to 2.0 parts of awetting agent selected from the group of essentially water solubleagents consisting of alkyl aryl sulphonates, alkyl sulphates and asulphonate resulting from the reaction of a fatty acid and an organicsulphonate, and the remainder water.

9. The process of etching a device composed of metals selected from thegroup consisting of zinc, magnesium, ZlIlC base alloys and magnesiumbase alloys consisting in said device having portions of its surfacecovered with an acid resisting coating to define a design and applyingan etching mixture to the remaining exposed or unprotected faces of thedevice with an etching mixture of between 3 to 20 parts by weight ofnitric acid, of between 1 to 12 parts by weight of a petroleum solvent,surface active agents consisting of between 0.02 to 2.0 parts by weightof an oil soluble alkyl aryl sulphonate and, of between 0.00008 to 2.0parts by weight of an essentially water soluble wetting agent, and theremainder water.

10. The process of etching a device composed of metals selected from thegroup consisting of zinc, magnesium, zinc base alloys and magnesium basealloys consisting in said device having portions of its surface coveredwith an acid resisting coating to define a design and applying anetching mixture to the remaining exposed or unprotected faces of thedevice with an etching mixture of between 3 to 20 parts by weight ofnitric acid, of between 1 to 12 parts by weight of a petroleum solvent,surface active agents consisting of .02 to 2.0 parts by weight of an oilsoluble alkyl aryl sulphonate and of between 0.00008 to 2.0 parts byweight of a wetting agent selected from the group of essentially watersoluble agents consisting of alkyl aryl sulphonates, alkyl sulphates anda sulphonate resulting from the reaction of a fatty acid and an organicsulphonate and the remainder water.

References Cited in the file of this patent UNITED STATES PATENTS2,176,423 Iaeger Oct. 17, 1939 2,640,764 Easley et al. June'2, 19532,640,766 Easley et a1. June 2, 1953 2,640,767 Easley et a1. June 2,1953 2,687,346 McDonald Aug. 24, 1954 2,750,340 Gerhardt June 12, 19562,762,694 Newman Sept. 11, 1956 UNITED STATES PATENT OFFICE CERTIFICATEOF CORRECTION Patent No 3,074,836 January 22 1963 Abraham Isidor Shereret al.,

It is hereby certified that error appears in the above numbered patentrequiring correction and that the said Letters Patent should read ascorrected below.

Column 6 line 3 for "0,2 to 2,0 parts" read 002 to 2.0 parts line 16 for"petaroleum-cut" read petroleum cut Signed and sealed this 31st day ofMarch 1964.,

E Ages t. V EDWARD J BRENNER ERNEST w, SWIDER Attesting OfficerCommissioner of Patents

1. A BATH SOLUTION FOR A ONE-STAGE QUICK ETCH ON AN ALLOY COMPRISING BYWEIGHT 3 TO 20 PARTS NITRIC ACID, 1 TO 12 PARTS OF A PETROLEUM SOLVENT,0.2 TO 2.0 PARTS LONG CHAIN ALKYL ARYL SULPHONATE AND 0.00008 TO 2.0PARTS ALKYL ARYL SUPHONATE HAVING A CHAIN LENGTH OF ABOUT 3 TO 12 CARBONATOMS, AND THE REMAINDER WATER.
 9. THE PROCESS OF ETCHING A DEVICECOMPOSED OF METALS SELECTED FORM THE GROUP CONSISTING OF ZINC,MAGNESIUM; ZINC BASE ALLOYS AND MAGNESIUM BASE ALLOYS CONSISTING IN SAIDDEVICE HAVING PORTIONS OF ITS SURFACE COVERED WITH AN ACID RESISTINGCOATING TO DEFINE A DESIGN AND APPLYING AN ETCHING MIXTURE TO THEREMAINING EXPOSED OR UNPROTECTED FACES OF THE DEVICE WITH AN ETCHINGMIXTURE OF BETWEEN 3 TO 20 PARTS BY WEIGHT OF NITRIC ACID, OF BETWEEN 1TO 12 PARTS BY WEIGHT OF A PETROLEUM SOLVENT, SURFACE ACTIVE AGENTSCONSISTING OF BETWEEN 0.02 TO 2.0 PARTS BY WEIGHT OF AN OIL SOLUBLEALKYL ARYL SULPHONATE AND, OF BETWEEN 0.00008 TO 2.0 PARTS BY WEIGHT OFAN ESSENTIALLY WATER SOLUBLE WETTING AGENT, AND THE REMAINDER WATER.